I would think he meant synthroid. But, I would call his office and ask him what he meant. He's one of THE Iodine docs. There are too many of us hypo folks taking dessicated thyroid meds WITH iodine.
I DO know that it is really hard to convert T4 only meds to T3 , it was for me anyway when I was on synthcrap. Dessicated thyroid meds CONTAIN iodine, in the form usable by the thyroid. I for one would like to know what the heck he meant too.